Wear-resistance of knitting machine support members

ABSTRACT

A support member for a plurality of reciprocable knitting elements of a knitting machine, said support member being formed with a plurality of selected surfaces upon which said knitting elements reciprocate, said support member being provided on the said selected surfaces thereof with a hardened nickel phosphide coating having a uniform thickness. The slots of the needle cylinder and/or dial member of a circular knitting machine are provided with said nickel phosphide coating. An electroless process for plating a wear-resistant nickel phosphide surface coating on at least the base and side walls of the slots of a ferrous element of a circular knitting machine, comprising sensitizing said surfaces by application thereto of an aqueous solution of a soluble tin salt and a weak acid until a film of tin is deposited over substantially the entire areas of said surfaces, preheating said element in an aqueous bath maintained at an elevated temperature, immersing said element in an aqueous plating solution containing a soluble nickel salt, a hypophosphite and a buffering agent, maintaining said plating solution at a temperature within the range of from 160* to 204*F., maintaining the phosphorous content of said plating solution within the range of from 9 to 11 weight percent, cyclically moving said element through said plating solution in such manner as to rotate same in substantially the plane of rotation through at least 90* per cycle, withdrawing said element from said plating solution when said film of tin has been replaced by a coating of a nickel-phosphorous compound and said coating has attained a uniform thickness, and subjecting said coated surfaces to hardening in a reductive environment at an elevated temperature not greater than substantially 750*F. for a period of time not substantially exceeding 1 hour.

Unite States Patent 1191 Flicker [451 May 13, 1975 1 1 WEAR-RESISTANCE OF KNITTING MACHINE SUPPORT MEMBERS [75] Inventor: Howard D. Flicker, Miami, Fla.

[73] Assignee: The Singer Company, New York,

22 Filed: Nov. 5, 1973 21 Appl. No.: 413,018

[52] U.S. Cl. 66/115 [51] Int. Cl B041) 15/00 [58] Field of Search 66/114, 115, 31; 1 17/130 B [56] References Cited UNITED STATES PATENTS 2,532,283 12/1950 Brewer et al.... 117/130 E 3,667,113 6/1972 Philip 66/115 FOREIGN PATENTS OR APPLICATIONS 849,529 11/1939 France 66/115 1,107,817 3/1968 United Kingdom 66/115 1,145,080 3/1969 United Kingdom 66/115 Primary Examiner-Ronald Feldbaum Attorney, Agent, or FirmRobert E. Smith; Marshall J. Breen; Chester A. Williams, Jr.

[57] ABSTRACT A support member for a plurality of reciprocable knitting elements of a knitting machine, said support member being formed with a plurality of selected surfaces upon which said knitting elements reciprocate, said support member being provided on the said selected surfaces thereof with a hardened nickel phosphide coating having a uniform thickness. The slots of the needle cylinder and/or dial member of a circular knitting machine are provided with said nickel phosphide coating. An electroless process for plating a wear-resistant nickel phosphide surface coating on at least the base and side walls of the slots of a ferrous element of a circular knitting machine, comprising sensitizing said surfaces by application thereto of an aqueous solution of a soluble tin salt and a weak acid until a film of tin is deposited over substantially the entire areas of said surfaces, preheating said element in an aqueous bath maintained at an elevated temperature, immersing said element in an aqueous plating solution containing a soluble nickel salt, a hypophosphite and a buffering agent, maintaining said plating solution at a temperature within the range of from 160 to 204F., maintaining the phosphorous content of said plating solution within the range of from 9 to 11 weight percent, cyclically moving said element through said plating solution in such manner as to rotate same in substantially the plane of rotation through at least 90 per cycle, withdrawing said element from said plating solution when said film of tin has been replaced by a coating of a nickel-phosphorous compound and said coating has attained a uniform thickness, and subjecting said coated surfaces to hardening in a reductive environment at an elevated temperature not greater than substantially 750F. for a period of time not substantially exceeding 1 hour.

19 Claims, N0 Drawings WEAR-RESISTANCE OF KNITTING MACHINE SUPPORT MEMBERS BACKGROUND OF THE INVENTION It was heretofore known to improve the wearresistance of surfaces subjected to repetitive frictional contact by treating such surfaces according to any of avariety of procuedures. For example, such surfaces might be carbo-nitrided, chromium-plated or flamehardened. However, each of such techniques occasioned certain disadvantages, particulaly where the surfaces to be hardened are located in relatively inaccesible regions such as on certain elements of a circular knitting machine. For example, liquid carbonitriding requires implimentation at elevated temperatures of the order of l550l600F. When the carbo-nitriding of low or mild carbon steel is conducted at lower temperatures, such as at approximately 1060F., the phenomenon is one primarily of nitriding. Since inadequate hardness resluts at the lower temperatures it is essential that the higher temperatures be maintained. However, in such event the part of the machine being treated is greatly distorted unless an alloy steel is employed capable of being air hardened. This latter expedient, however, results in prohibitive increased costs so that recouse is made to the high-temperature treatment and to straightening out the distorted case-hardened part. Frequently it is not possible to remove all of the distortion. The consequence is either a high scrap loss or an inferior machine. Further, the cyanide salts used in the process must be aged to function properly. This requires the allocation of a certain amount of down-time during the manufacturing process which has been found intolerable in view of the desire to maintain tight production schedules.

Chromium electroplating has been found disadvantageous particularly in connection with the hardening of the surfaces of the slots of needle cyclinders and dial members of circular knitting machines. Since the extent of chromium plate developed depends principally upon the amount of current which reaches the cathode surfaces, and because practically no current reaches the base of the slot due to diversion by the walls of the slot, substantially no chromium is deposited on the base of slot where it is most needed. Also, it is characteristic of chromium electroplating that the deposit builds up on the corners of the part, forming balls and trees- [at such locations and thereby precluding the development of an actual plating thickness greater than approximately 0.0003 inches without closing in and creating rough surfaces at the lead corners of, for example, the slot of a needle cylinder or dial member.

Flame hardening and induction hardening suffer from problems perculiar to such techniques such as extremely high material cost and major distortion for the former and the need to utilize special cutting tools or repeated replacement of such tools with the latter technique.

In view of the shortcomings of the surface-hardening techniques just discussed, the art of knitting machine manufacture turned to the process of electroless plating for a satisfactory resolution of the problem. Typical of such procedures were the teachings found in the Gutzeit et al., U.S. Pat. Nos. 2,658,841 and 2,658,842 both granted Nov. 10, 1953 and the Robert A. Spaulding U.S. Pat. Nos. 2,276,968 and 2,726,969 both granted Dec. 13, 1955. The Gutzeit et al patents taught the electroless nickel plating of catalytic material by subjecting the catalytic material to a plating solution which generally comprises an aqueous bath containing the proper proportions of nickel ions, hypophosphite ions and a buffer. The higher numbered Gutzeit et al. patent taught the utility of particular buffering agents, i.e. soluble salts of short chain aliphatic dicarboxylic acids so as to prevent a decrease in the pH of the plating solution with its attendant adverse effects upon the plating process. Spaulding, in an attempt to prevent an adverse change in the pH and to reduce the level of phosphite in the plating solution, suggested in U.S. Pat. No. 2,726,968 that the solution be contacted with an anionic exchange material. The second Spaulding patent teaches the addition of a water-insoluble nickel salt when more nickel is required during the plating process. An alkaline radical is thus liberated in the solution which tends to prevent a lowering of the pH and also inhibits the formation of chloride products.

Prior plating procedures were not capable of developing a consistently hard surface coating characterized by a Rockwell C-scale hardness of at least 70. When utilizing conventional electroless nickel plating techniques, although hardening steps were employed, such as baking at approximately 750F., the resultant hardness nevertheless varied from 63 to 72. The surfaces of certain knitting machine elements require much greater hardness in order to withstand the degree, of wear to which they are subjected over an extended period of time. The slots of the needle cylinder and dial member and the surfaces of the sinker rest ring which support the sinkers are surfaces which are particularly affected by continued frictional contact and which require a hard slippery protective surface coating. Further, it was not possible heretofore to produce a smooth surface of the plated material where a relatively thin coating was desired. Electroless nickel characteristically deposited initially in the form of tiny spheres which, as the proces proceeded, fused together to form the surface. However, the final surface of thin coatings never attains the requisite degree of smoothness. In actual practice the spheres frequently separated from the base metal and functioned as an abrasive. Still further, it was not possible to coat the slots of the needle cylinder and dial member so as to produce a surface in which the dimensions of the coating were uniform at the base of the slot and on the side walls thereof. Other disadvantages existed as are well known to persons skilled in the art.

SUMMARY OF THE INVENTION It is one object of the present invention to provide a circular knitting machine in which at least the needlebearing surfaces of the needle accommodating slots of the needle cylinder thereof are given a wear-resistant coating of a non-ferous metal.

It is another object of the present invention to provide a circular knitting machine in which the needle accommodating slots of the needle cylinder and/or dial member thereof are given a wear-resistant nickel phosphide surface coating of substantially uniform thickness at the base and side walls thereof having a uniform Rockwell C-scale hardness of at least 70. It is a further object of the present invention to provide the sinkersupporting surfaces of the sinker rest ring of a circular knitting machine with a wear-resistant nickel phosphide surface coating of substantially uniform thickness have a uniform Rockwell C-scale hardness of at ciprocable knitting elements ofa knitting machine with t a hardened nickel phosphide coating having a Rock well C-scale hardness of at least 70. According to the present invention there is provided a needle cylinder for a circular knitting machine having a plurality of needle accommodating slots therein, the needlebearing base of each of said slots being provided with a wear-resistant, non-ferrous metal coating of substan-. tially uniform thickness, said coating being bonded to the substrate by means of a network of interstices in the surface thereof. According to the present invention there is provided a dial member for a circular knitting machine having a plurality of needle accommodating slots therein, the needle-bearingbase of each of said slots being provided with a wear-resistant, non-ferrous metal coating of substantially uniform'thickness, said coating being bonded to the substrate by means of a network of interstices in the surface thereof.

According to the present invention there isalso provided in a circular knitting machine comprising a needle cylinder having a plurality of needle accommodating slots extending generally axially thereof, a plurality of cam section blocks arranged about said needle cylin-.

. develop a smooth, hardsurface coating of uniform thickness even within the narrow needle accommodatv ing slots "of the needle cylinder and dial member of a circular knitting machine where, for example,,such

der and provided with means adapted to impart move- I ment to the needles carried reciprocably in said slots, means for feeding yarn to said needles, and means for providing relative rotational movement between said cylinder and said section blocks, the improvement comprising a hardened nickel phosphide surface coating on at least the base and side walls of said slots, said coating having a substantially uniform thickness.

According to the present invention there is further provided a support member for a plurality of reciprocable knitting elements of a knitting machine, said support member being formed with a plurality of selected surfaces upon which said knitting elements reciprocate, said support member being provided on the said selected surfaces thereof with a hardened nickel phosphide coating having a substantially uniform thickness.

According to the present invention there is still further provided an electroless process for plating a nickel phosphide surface coating on at least the needle contacting surfaces of a ferrous element of a knitting machine adapted to guide a plurality of needles for reciprocatory movement across said surfaces, comprising (a) subjecting said surfaces to a precleaning procedure for the removal of burrs and surface contaminants; (b) sensitizing said surfaces by applying theretoanaqueous' solution of a soluble tin salt and a weak acid until a film of tin is deposited over substantially the entire areas of said surfaces; (c) preheating said element in an aque ous bath maintained at an elevated temperature; ((1) immersing said elememt in an aqueous plating solution containing a soluble nickel salt, a hypophosp'hite salt and a buffering agent, maintaining said solution at a temperature within the range of from 160 to 204F.,

maintaining the phosphorous content of said solution i within the range of from 9 to ll weight percent, cyclically moving said elements through said plating solutions in such manner as to rotate same in substantially V I the plane of rotation through at least per cycle; (e) withdrawing said element from said plating salmon. when said film of tin has been replaced by a coating of a nickelphosphorous compound and said coating has" attained a uniform thickness; (f) and subjecting Isaiah coated surfaces to hardening in a reductiv e.;environment at an elevated temperature not greater thansub- I f I stantially 750F. for a period of time not substantially? exceeding l hour,

DETAILED DESCRIPTION OF THE INVENTION It has been found that surfaces of a knittingbmachine member which are subjected to the wear occasioned by the reciprocation of certain knitting elements, particu- I larly the knitting needlesand sinkers thereof, canbe treated to become more wear-resistant. By following a particular process for electroless plating it is possible to slots may be asthin as 0.012 inches intwidth and 0.338 inches deep. A coating can be developed which consischemical deburring as is well known; .Oncethe part is deburred itis customary to directa strong stream of air and/or steam over the part to remove anyresidualmafi terial which may remain. This is of particular impory tancewhere the surfaces to be coatedare within the T slots of a needle cylinder or dial member since thereis a tendency for material to accumulate along the base lines of such slots which would prevent the subsequent 1 deposition of a continuous coatingthroughout the slot. W The part is also generally degreased to effect the re- A moval of any, grease or oil film, which may be'present. Alternativ.ely,1or in addition to the degreasing step, the t part may be alkaline cleaned to emulsify any grease;

present and to deep clean into the minute crevices in l s the face of the part.

Once the part has been precleaned the next step in the process oftthe invention is the sensitizing of theareai v V to be, coated. This step is not to be confused with the erably hydrochloric acid, and water is applied tothe surfaces to be coated. A suitable solution-hasibeen found to be the admixture of "5 pounds of stannous chloride, 50 gallons of hydrochloric acid and SOgallons I of waterLl-Iowever, from 2-10 pounds ofstannous chlo ride per gallons of acid mix, i.e., from 20 to 100" I percent acid, has been found to be satisfactoryv It will be appreciated, of course, that'other metalliclsalts may be us edin which the metal isabove iron in the electromotive series; however, in order to function effectively. I inthe sensitizing solution the salt must be capable of tently exhibits a Rockwell C-scale hardness of at least The initial step in the process of this invention is one of precleaning, Any of the conventional procedures for t I, accomplishing this objective are suitable; Thus, a wire brush may be employed to remove any burrs which I may be present on the surfaces of the knitting machine r partwhichis to be plated. Alternatively, the part can I be subjected to abrasive blasting, glass bead blasting or forming an autocatalytic coating on the substrate and of not poisoning the plating solution. The salt should be relatively unstable in liquid solution such that a film of the metal is deposited in molecularly thin dimensions upon the surface being treated as part of the surface crystal lattice. Other metallic salts contemplated as being operative are aluminum chloride and palladium chloride.

Although applicant does not wish to be bound by any particular theory it is presently believed that when the ferrous element is immersed in the sensitizing solution a galvanic reaction occurs which results in the displacement of iron atoms by tin. Subsequently, during the plating step, to be hereinafter described, it is thought that the tin sets up a galvanic cell with the nickel of the plating solution thereby resulting in production of an anodic current which leads to the introduction of nickel into the structure of the surface crystals of iron. The deposition and adhesion of the nickel occurs uniformly over the entire surface being treated. Hence, the plating process begins uniformly and the coating develops to a uniform thickness or depth on the bases of slots as well as on their side walls. A spectrographic analysis of the element following sensitizing has determined that a film of tin of no more than several millionths of an inch in thickness was deposited uniformly over the entire surface both in recessed areas as well as on readily accessible exposed areas.

The sensitizing step should desirably be continued at ambient temperature, preferably within the range of from 70-90F., until substantially the entire surface being treated has been coated with a film of tin to a depth measuring in the millionths of an inch. It has been found that depending upon the particular alloy being treated and the surface characteristics of the part the sensitizing step should be carried out for a period of time ranging from seconds to 2 minutes. Temperatures exceeding 100F. should be avoided since there is a tendency for the solution to attack the base metal at such elevated temperatures.

Once the sensitizing step has been completed the element is subjected to a preheating procedure. It has been found eminently satisfactory to immerse the element for at least one-half hour in a hot water bath prior to immersion in the plating solution. order to promote better adhesion and a smoother coating preheating should be conducted at a temperature which approximates the temperature of the subsequent plating bath. Tests have revealed that the tin film is not removed in the preheating step; this would indicated that there is adhesion to the substrate. It will be understood, of

course, that although the use of a hot water bath is presently preferred other techniques may be employed which avoid contamination of the part being treated and which will insure heating of the part below the exterior surface thereof.

Following preheating, the part to be plated is immersed in an electroless aqueous plating solution containing a nickel salt and sufficient hypophosphite reducing agent to reduce the nickel salt to metallic nickel. The basic reactions in connection with the deposition of nickel from such chemical reduction plating solutions are well known and need not be set forth herein.

It has been known to include a buffering agent in the plating solution in order to maintain some control over the production of reaction products and changes in solution pH which adversely affect the deposition of nickel or the form of the nickel deposited. In carrying out the present invention it has been found extremely beneficial to utilize a salt of propionic acid, i.e., propionic acid(2-hydroxyl) as the buffering agent. It may be prepared by admixing 60 g/L sodium hydroxide, 22 g/L propionic acid and 2 g/L cobalt acetate. The solution is titrated, and the sodium salt of propionic acid obtained is incorporated in the plating solution in an amount of from 10 to 30 g/L, the preferred amount being 20 g/L.

It has also been found that the addition of 0.05 g/L of oleyl alcohol, which performs as a nonionic wetting agent, enhances the plating process since it assures wetting to the bottoms of the slots of the article being treated. If the surface being treated is broad and flat then the inclusion of a wetting agent is not particularly needed. When employed, however, a concentration in the range of from 1:40 to 1:10 g/L has been found to be effective.

During the plating step the pH of the (solutions should be maintained within the range of from 4.7 to 4.9. This may be accomplished by the periodic addition of ammonium hydroxide or sulphuric acid as required depending upon whether the pH requires modification towards the alkaline or acid range. It has been determined that in order to obtain the desired final coating composition of nickel phosphide the phosphorous content of the plating solution should be maintained within the range of from 9-1 1%. changes in the pH level during plating affects the phosphorous content of the solution; thus it is important that the pH of the solution be closely monitored throughout the plating step.

To provide the requisite nickel for deposition it has been found that nickel salt which is soluble in aqueous solution is preferred. Of the various nickel salts which may be utilized nickel chloride is preferred. Nickel sulfate may be alternately employed, however, it has been found to be somewhat less efficacious for various reasons. From 18 to 60 g/l of the nickel salt has been found to provide sufficient nickel for the plating step. In order to reduce the nickel salt to metallic nickel the solution should contain a sufficient amount of hypophosphite. This is achieved by providing a suitable quantity of sodium hypophosphite. Further, although as little as 1.8 g/l of the hypophosphite will effectuate reduction of the nickel salt it is preferred to employ at least 5 g/l and up to 35 g/l in order to insure an adequate supply of phosphorous so that the coating will develop the requisite hardness during the final hardening step.

During the plating step the temperature of the plating solution is maintained within the range of from l60to 204F. Preferably the temperature is maintained between to F. Within the stated temperature ranges it will be appreciated that the rate of nickel deposition increases with a corresponding increase in solution temperature.

It has been found that in the plating of articles such as the slots of the needle cylinder or dial of a circular knitting machine, the base and side walls of which slots are relatively inaccessible, greatly improved results are obtained by providing for relative motion between the article and the plating solution. Desirably such relative motion is achieved by the cyclical to and fro movement of the article in the solution. At the end of each cycle the article is rotated approximately 90 in the plane of rotation. Such relative motion between the article and the plating solution insures an adequate supply of the solution to all internal surfaces of the slots. In the past it has been customary to agitate the solution either through the use of an air stream or by mechanical means; however, the geometry of the slotted articles is such that agitation by air streams has proven ineffective and, when mechanical agitation has been employed whereby the article is moved toand. fro within the plating solution, fresh liquid has been directed into those slots which are in line with the direction ofmovement whereas a substantially reduced supply of fresh liquid is directed into those slots located at substantially 90 to the path of movement of the article. The plating step is continued until a coating of the desired uniform thickness comprising nickel phosphide is formed upon the areas to be treated. Desirably the nickel phosphide coating thus formed will contain from 3 to 14 weight percent phosphorous. A thickness of at least 0.002 inches for the coating has been found to be effective when the substrate is a low carbon steel with a compression strength of less than 60,000 psi. It will be un-. derstood that with substrates which possess higher compressive strengths the thickness of the coating may be reduced.

The final step in the sequence of electroless nickel plating according to this invention is hardening of the coating composition which has been deposited upon. the surfaces. The article issubjected to an elevated temperature for a period of time sufficient to raise the temperature of the substrate to substantially 750F. Generally one-half hour has been found to be sufficient. The coating is then permitted to absorb hear from the substrate for approximately an additional onehalf hour. It has been found that by permitting the coated surface to absorb heat fromthe. substrate at such temperature for more than the additional one-half hour some degree of annealing takes place which results in a loss of hardness below the Rockwell C-scale hardness of 70. Thus, although the article comprising the base and coating have been subjected to the elevated temperature for only one-half hour, continued heating ofthe coating occurs through conduction of heat from the hot substrate thereto. Preferably the coating should be hardened to a Rockwell C-scale hardness of at least 70 where a low carbon steel substrate is coatedHowever, it is within the contempla tion of this invention to employ a solid lubricant on the plated surface. In such instances a lower hardness value for the coating may be sufficient. Also, the particular chemical composition of the coating may permit the hardness to be reduced. The process of this invention, however, leads to the production of coatings which have predictably consistent values. Further, the coating should be subjected to the elevated temperature under such conditions that there islittle or no oxidation of the phosphorous in the coating composition. The hardening step, therefore, should be conducted in a nonoxidizing environment. Preferably this environment is provided by placing the article in a suitably furnace together with a reducing agent which will combine with the free oxygen present and be inert with respect to the nickel phosphide coating composition. Preferably a supply of charcoal is placed in the furnace. It has been found that l pound of charcoal per 40 cubic feet of air within the furnace is quite effective in preventing oxidation of the phosphorous in the coating.

The following example is illustrative of the invention:

The needle cylinderof a circular knitting machine having a cut of 1680 slots in which the slot dimensions were 0.021 to 0.022 inches wide, 0. inches deep and 0.563 inches long was wire brushed for removal of,

burrs, airj cleaned to remove residual material inthe slots, and degreased. The cylinder was completely masked except for the baseiand side walls of'thesl'ots.

having the fol A sensitizing solution was prepared lowing ingredients? Stannous Chloride 5 lbs. Hydrochloric Acid 50 gallons. Water 50 gallons 7 I The aforesaid needle cylinder was immersed'in aibat h i of thesensitizing solution whichwas maintained at a v temperature of 80F. After one-half minute the needle I I cylinder was removed. from the bath. A filmyof'tin was deposited uniformly over the base and side walls ofthe a cylinder slots. I

The needle cylinder was immersed in a hot water bath which was maintainedat a temperature of FQ. After one-half hour the cylinder was removed from the bath.

An aqueous plating solutionwas prepared by admixing the following ingredients with water in the amounts specified:

Nickel chloride Sodium hypophosphite To theforegoing was added 20g/l of the salt I of propionic acid which was prepared as follows:.:

Sodium hydroxide in the amount of 60g/l was admixed with 22g/l of propionic acid and with 2gll of cobalt acetate to form a solution. The solution was. titrated, and thesodium. salt withdrawn wasaddedj to the plating solution; v The needle cylinder was then immersed in the plating solution which was introduced into a vinyl envelope within a steel tank. The steel tank was itself positioned within another steel shell A layer of ethylene glycol was.

interposedbetween the two steel sheels, and immersion heaters were inserted into the ethylene glycol/Filtering of the. solution was effected by means of an acid resistant pump with ceramic impellers. The solution was forced through polypropylene bags having 5 micron openings. Three such bags were. used, one within .the

other. The bags were washed regularly innitricacidto remove the nickel which was deposited in the pores or i interstices. The. vinyl liners were disposed of after approximately 3 days to avoidthe accumulation of nickel powder which would become the nucleus for plate-out,

thereby destroying the effectiveness of the mixture,

The plating solution was maintained at a temperature 7 I of F. and the pH was regulated between the limits of 4.7 to 4.9 for a period of3 hours. At the end ofthis' was removed from the furnace and the slots were inspected. The base and side walls of each of the slots' were found to have a smooth coatingofnickel phos phide of uniform depth over such areas. The coating had a Rockwell C-scale hardness. of 70.

The needle cylinder was placed in experimental use for a period of 24 months, the cylinder being incorporated in a circular knitting machine which was in production the major portion of each work day. At the end of the experimental period it was determined that the failure rate attained by the needle cylinder having its slots coated in accordance with the present invention was only 2.3 percent as compared with a failure rate of more than twice this amount experienced with needle cylinders not treated in accordance with the present invention.

The coating developed by the electroless nickel plating procedure heretofore described consistently exhibits the desired Rockwell C-scale hardness, has the required degree of lubricity, is uniformly deposited over the surfaces to be treated, and has been found to be particularly effective when formed on the base and side wall surfaces of the slots of needle cylinders and dial members of circular knitting machines. However, as indicated above, the coating may be developed on selected surface areas of support members such as the sinker rest ring of the machine or the flat bed of a flat bed knitting machine which area are designed to support, for example, the sinkers or knitting needles respectively. The service life of such parts has thus been increased drammatically as a result of the application of the coating according to this invention.

It will be understood that various changes in the details, materials, arrangements of parts, and operating conditions which have been herein described and illustrated in order to explain the nature of the invention, may be made by those skilled in the art within the principles and scope of the invention.

Having thus set forth the nature of the invention, what is claimed herein is:

l. A needle cylinder for a circular knitting machine having a plurality of needle accomodating slots therein, the needle-bearing base of each of said slots being provided with a wear-resistant non-ferrous metal coating comprising nickel phosphide which exhibits a Rockwell C-scale hardness of at least 70 and is of substantially uniform thickness of at least 0.002 inches, said coating being bonded to the substrate by means of a network of interstices in the surface thereof.

2. A needle cylinder according to claim 1, wherein each of said slots includes a uniformly spaced sidewalls and a base which joins each such sidewall in a fillet of which the cross-sectional configuration is substantially uniform along said slots, said coating having been deposited by a physicochemical process and not appreciably altering the cross-sectional shape of said fillets.

3. A dial member for a circular knitting machine having a plurality ov needle accommodating slots therein, the needle-bearing base of each said slots being provided with a wear-resistant non-ferrous metal coating comprising nickel phosphide which exhibits a Rockwell C-hardness of at least 70 and is of substantially uniform thickness of at least 0.002 inches said coating being bonded to the substrate by means of a network of interstices in the surface thereof.

4. A dial member according to claim 3, wherein each of said slots includes uniformly spaced sidewalls and a base which joins each such sidewall in a fillet of which the cross-sectional configuration is substantially uniform along said slots, said coating having been deposited by a physicochemical process and not appreciably altering the cross-sectional shape of said fillets.

5. A support member for a plurality of reciprocable knitting elements of a knitting machine, said support member being formed with a plurality of selected surfaces upon which said knitting elements reciprocate, said support member being provided on the said selected surfaces thereof with a hardened nickel phosphide coating.

6. A support member according to claim 5, wherein said selected surfaces comprise a plurality of knitting needle accommodating slots, each of said slots including uniformly spaced sidewalls and a base joining each such sidewall in a fillet of which the cross-sectional configuration is substantially uniform along said slots, said nickel phosphide coating not appreciably altering the cross-sectional shape of said fillets.

7. A support member according to claim 6, wherein said coating is smooth and of uniform thickness throughout.

8. A support member according to claim 6, in the form of a circular knitting machine needle cylinder.

9. A support member according to claim 8, wherein said coating has a thickness of at least 0.002 inches.

10. A support member according to claim 8, wherein said coating has a Rockwell C-scale hardness of at least 70.

11. A support member according to claim 6 in the form of a circular knitting machine dial cylinder.

12. A support member according to claim 11, wherein said coating has a thickness of at 'least 0.002 inches.

13. A support member according to claim 11, wherein said coating has a Rockwell C-scale hardness of at least 70.

14. A support member according to claim 6 in the form of a circular knitting machine sinker rest ring.

15. A support member according to claim 14, wherein said coating has a thickness of at least 0.002 inches.

16. A support member according to claim 14, wherein said coating has a Rockwell C-scale hardness of at least 70.

17. A support member according to claim 6 in the form of the flatbed of a flatbed knitting machine.

18. A support member according to claim 17, wherein said coating has a thickness of at least 0.002 inches.

19. A support member according to claim 17, wherein said coating has a Rockwell C-scale hardness of at least 70. 

1. A NEEDLE CYLINDER FOR A CIRCULAR KNITTING MACHINE HAVING A PLURALITY OF NEEDLE ACOMODATION SLOTS THEREIN, THE NEEDLEBEARING BASE OF EACH OF SAID SLOTS BEING PROVIDED WTH A WEARRESISTANT NON-FERROUS METAL COATING COMPRISING NICKEL PHOSPHIDE WHICH EXHIBITS A ROCKWELL C-SCALE HARDNESS OF AT LEAST 70 AND IS OF SUBSTANTIALLY UNIFORM THICKNESS OF AT LEAST 0.002 INCHES, SAID COATING BEING BONDED TO THE SUBSTRATE BY MEANS OF A NETWORK OF INTERSTICES IN THE SURFACE THEREOF.
 2. A needle cylinder according to claim 1, wherein each of said slots includes a uniformly spaced sidewalls and a base which joins each such sidewall in a fillet of which the cross-sectional configuration is substantially uniform along said slots, said coating having been deposited by a physicochemical process and not appreciably altering the cross-sectional shape of said fillets.
 3. A dial member for a circular knitting machine having a plurality ov needle accommodating slots therein, the needle-bearing base of each said slots being provided with a wear-resistant non-ferrous metal coating comprising nickel phosphide which exhibits a Rockwell CQ-hardness of at least 70 and is of substantially uniform thickness of at least 0.002 inches said coating being bonded to the substrate by means of a network of interstices in the surface thereof.
 4. A dial member according to claim 3, wherein each of said slots includes uniformly spaced sidewalls and a base which joins each such sidewall in a fillet of which the cross-sectional configuration is substantially uniform along said slots, said coating having been deposited by a physicochemical process and not appreciably altering the cross-sectional shape of said fillets.
 5. A support member for a plurality of reciprocable knitting elements of a knitting machine, said support member being formed with a plurality of selected surfaces upon which said knitting elements reciprocate, said support member being provided on the said selected surfaces thereof with a hardened nickel phosphide coating.
 6. A support member according to claim 5, wherein said selected surfaces comprise a plurality of knitting needle accommodating slots, each of said slots including uniformly spaced sidewalls and a base joining each such sidewall in a fillet of which the cross-sectional configuration is substantially uniform along said slots, said nickel phosphide coating not appreciably altering the cross-sectional shape of said fillets.
 7. A support member according to claim 6, wherein said coating is smooth and of uniform thickness throughout.
 8. A support member according to claim 6, in the form of a circular knitting machine needle cylinder.
 9. A support member according to claim 8, wherein said coating has a thickness of at least 0.002 inches.
 10. A support member according to claim 8, wherein said coating has a Rockwell C-scale hardness of at least
 70. 11. A support member according to claim 6 in the form of a circular knitting machine dial cylinder.
 12. A support member according to claim 11, wherein said coating has a thickness of at least 0.002 inches.
 13. A support member according to claim 11, wherein said coating has a Rockwell C-scale hardness of at least
 70. 14. A support member according to claim 6 in the form of a circular knitting machine sinker rest ring.
 15. A support member according to claim 14, wherein said coating has a thickness of at least 0.002 inches.
 16. A support member according to claim 14, wherein said coating has a Rockwell C-scale hardness of at least
 70. 17. A support member according to claim 6 in the form of the flatbed of a flatbed knitting machine.
 18. A support member according to claim 17, wherein said coating has a thickness of at least 0.002 inches.
 19. A support member according to claim 17, wherein said coating has a Rockwell C-scale hardness of at least
 70. 